Ultrafine Hydrous Kaolin Pigments, Methods of Making the Pigments, and Methods of Using the Pigments in Gloss Paint Formulations

ABSTRACT

Disclosed are methods of processing kaolin to produce ultrafine hydrous kaolin. The methods involve processing gray crude kaolin by subjecting the kaolin crude to flotation and then centrifuging the kaolin to provide a fine stream that is subject to refinement. Also disclosed are systems for the automated processing of gray crude kaolin to produce the ultrafine hydrous kaolin and paint compositions that contain the ultrafine hydrous kaolin.

FIELD OF THE INVENTION

The present invention generally relates to ultrafine kaolin pigments,making ultrafine kaolin pigments from the gray crude kaolin, and usingthe ultrafine kaolin pigments in paint compositions.

BACKGROUND OF THE INVENTION

Kaolin is a fine usually white clay formed by the weathering ofaluminous minerals (as feldspar) and mainly consists of kaolinite.Kaolinite is commonly represented by one or more of the chemicalformulae Al₄Si₄O₁₀(OH)₈; Al₂O₃·2SiO₂·2H₂O; and/or Al₂Si₂O₅(OH)₄. Kaolinis one of the many industrial minerals mined today. Reserves are foundin Georgia (USA), Egypt, Brazil, United Kingdom, Queensland (Australia),Korea, China, and Ukraine.

Generally speaking, kaolin from different countries, and even differentdeposits within the same country, differs in many respects due tovariations in a number of kaolinite properties. Examples of suchproperties include degree of crystallinity, coarseness, brightness,levels of other compounds such as titania and iron oxide, particle size,particle shape, size and/or shape distribution. Variations in propertiesleads to differences in performance of the resultant kaolin products.For example, crystallinity impacts resultant brightness, whiteness,opacity, gloss, and viscosity of the resultant products. It is notedthat opacity and gloss are application performance parameters while theother listed parameters are pigment attribute parameters. Particle size,shape, and distribution impacts the smoothness, optical properties, andflow properties of the resultant products. Smoothness and opticalproperties are application performance parameters while flow propertiesare pigment attribute parameters.

Kaolin based products are used in many applications including paints,paper coatings, agricultural compositions, fiberglass products, polymerand rubber compositions, ceramic applications, catalyst supports,pharmaceuticals, cosmetics, electrical components, adhesives, filteraids, and many more. Certain grades of kaolin having discrete propertiesare ideally suited for select applications. Accordingly, to maximize thequality of a resultant kaolin grade, kaolin crude is subjected toprocessing that yields a specifically desired grade of kaolin.

The paint industry supplies consumer-oriented products of the solventand emulsion types. Solvent or so-called “oil based” paints arerelatively simple systems, easy to formulate but difficult for theconsumer to use. Solvent paint contains a binder (oil of resin), asolvent (thinner), drying agents and pigments. Alkyd paint is the mostcommon kind of oil based paint, and many oil based paints are thereforenormally referred to as alkyd paints. Alkyd is simply the name of thesynthetic resin, usually containing a vegetable oil, that is used as thebinder. Emulsion or so-called “latex” paints are complex mixturescontaining latex surfactants, protective colloids, emulsifiers and waterin addition to one or more types of pigment. Following theirintroduction after World War II, latex paints have substantially gainedin market acceptance. Latex paints now account for a majority ofinterior and exterior paint trade sales.

Interior and exterior paints have generally similar formulations. Animportant distinction, however, is that exterior grade paints containrelatively more binder and prime pigment but less extender pigment thaninterior paints. This is because paint film integrity and overalldurability are more critical in exterior paints than in interior grades.Accordingly, improved pigments and extender pigments are desired forexterior paints.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is intended toneither identify key or critical elements of the invention nor delineatethe scope of the invention. Rather, the sole purpose of this summary isto present some concepts of the invention in a simplified form as aprelude to the more detailed description that is presented hereinafter.

The present invention provides ultrafine kaolin pigments that have atleast one of high surface area, fine particle size distribution, low oilabsorption, and high GE brightness values. Waste is mitigated whenmaking the ultrafine kaolin pigments, because selective flocculation isnot performed on the crude kaolin starting material. Moreover, unusedcoarse pigments produced as a by-product while making the ultrafinekaolin pigments may be advantageously used in paper coatingapplications. Due to the high surface area, fine particle sizedistribution, low oil absorption, and high GE brightness values of theultrafine kaolin pigments, they are ideally suited for paintformulations, especially gloss paint compositions.

One aspect of the invention relates to methods

Another aspect of the invention relates to

To the accomplishment of the foregoing and related ends, the inventioncomprises the features hereinafter fully described and particularlypointed out in the claims. The following description and the annexeddrawings set forth in detail certain illustrative aspects andimplementations of the invention. These are indicative, however, of buta few of the various ways in which the principles of the invention maybe employed. Other objects, advantages and novel features of theinvention will become apparent from the following detailed descriptionof the invention when considered in conjunction with the drawings.

BRIEF SUMMARY OF THE DRAWINGS

FIG. 1 is a flow diagram of one aspect of a system and method ofprocessing kaolin in accordance with the present invention.

FIG. 2 is a schematic diagram of another aspect of a system forautomated processing of kaolin in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The methods of the present invention enable the efficient production ofultrafine hydrous kaolin from gray kaolin crude. The ultrafine hydrouskaolin is advantageously employed in paint compositions. The methods ofthe present invention also enable the production of coarse engineeredkaolin for paper applications as a by product of making the ultrafinekaolin. Ultrafine kaolin pigments are characterized by low oilabsorption, high brightness, high surface area, at least 96% by weightof the particles have a size of about 1 micron or less, and at least 97%by weight of the particles have a size of about 2 microns or less.Coarse engineered kaolin pigments are characterized by low surface area,at least 80% by weight of the particles have a size of about 2 micronsor less, and narrow particle size distribution.

The methods of the present invention involve subjecting gray kaolincrude to floatation and then high speed centrifugation in a sequentialmanner to provide the ultrafine kaolin. Degritting may be optionallyperformed before flotation while ozonation may be optionally performedafter flotation and before high speed centrifugation. In one embodiment,the gray kaolin crude or the degritted gray kaolin crude is notsubjected to selective flocculation. Sequential means that flotation andcentrifugation are performed in the order listed, although optionallyother acts may be performed before, during and/or after the twosequential acts (such as degritting and/or ozonation and/or refinement).

The kaolin crude that can be subjected to the methods of the presentinvention contains a super-major amount of gray or hard kaolin,optionally a minor amount of fine white kaolin, and optionally smallamounts of nonkaolin particles. Generally, gray kaolins have a high ironcontent. Nonkaolin particles include titania, quartz, variousferruginous minerals, mica, and nonkaolinitic clays such as bentoniteand attapulgite. Super-major amounts include at least 75% by weight,minor amounts include less than 50% by weight, and small amounts includeless than 10% by weight. In another embodiment, the kaolin crudecontains at least about 80% by weight of gray or hard kaolin and lessthan about 20% by weight of fine white kaolin. In yet anotherembodiment, the kaolin crude contains at least about 90% by weight ofgray or hard kaolin and less than about 10% by weight of fine whitekaolin.

The kaolin crude contains particles wherein at least about 70% by weighthave a particle size of about 2 microns or less, at least about 30% byweight have a particle size of about 0.3 microns or less, a titaniacontent from about 1% to about 3% by weight, and a surface area of atleast about 18 m²/g. In another embodiment, the kaolin crude containsparticles wherein at least about 80% by weight have a particle size ofabout 2 microns or less, at least about 35% by weight have a particlesize of about 0.3 microns or less, a titania content from about 1.5% toabout 2.5% by weight, and a surface area of at least about 20 m²/g.

Prior to processing the kaolin crude, a slurry may be formed bycombining the kaolin crude with water, and optionally a dispersant. Oneadvantage to the present invention is that a dispersant may not berequired before an ultrafine stream of hydrous kaolin is separated fromcoarse kaolin via high-speed contrifugation. Thus, in one embodiment, adispersant is not employed until an ultrafine stream of hydrous kaolinis separated from coarse kaolin via high-speed contrifugation.

The dispersant may be an organic dispersant or inorganic dispersant.Inorganic dispersant typically include phosphate salts. Examples ofphosphate salts include inorganic polyphosphates and pyrophosphates(which are actually a type of polyphosphate), such as sodiumhexametaphosphate (SHMP), sodium tripolyphosphate (STPP) and tetrasodiumpyrophosphate (TSPP).

Organic dispersants typically include ammonia-based dispersants,sulfonate dispersants, carboxylic acid dispersants, and polymericdispersants, such as polyacrylate dispersants, as well as other organicdispersants conventionally employed in kaolin pigment processing.

The kaolin crude is optionally subjected to degritting. Kaolin crudeoccurs as an ore that may contain grit, grit composed a relatively largeparticles. The grit is undesirable and thus is removed. The resultingdegritted crude kaolin is composed largely of kaolin particles thatusually have a wide range of sizes ranging from slimes (finer than 0.3microns) up to about 15 microns.

Degritting is performed in any conventional manner using one or more ofsieves, sandboxes, gravity settling, or hydrocyclones. Either wet or drydegritting may be employed. For example, degritting may be performed bycombining the crude kaolin with water and passing the slurried mixturethrough a sieve, such as a 325 mesh sieve or a 200 mesh sieve.Optionally, a clay dispersant is also added to the slurry to provideadditional fluidity to facilitate the degritting process. Examples ofclay dispersants include ammonia-based dispersants, phosphate-baseddispersants, sulfonate dispersants, carboxylic acid dispersants, andpolymeric dispersants, such as polyacrylate dispersants, as well asother organic dispersants employed in kaolin pigment processing. Theamount of dispersant used in the slurry is typically from about 0.01% toabout 1% based on the weight of crude kaolin.

After degritting the crude kaolin, the resulting degritted crude kaolinis subjected to flotation. Flotation serves to reduce the titaniacontent to less than about 1% by weight and/or reduce the iron oxidecontent to less than about 1.5% by weight. In another embodiment,flotation reduces the titania content to less than about 0.7% by weightand/or reduce the iron oxide content to less than about 1.25% by weight.In yet another embodiment, flotation reduces the titania content to lessthan about 0.5% by weight and/or reduce the iron oxide content to lessthan about 1% by weight. In still yet another embodiment, flotationreduces the titania content to less than about 0.4% by weight and/orreduce the iron oxide content to less than about 0.75% by weight. Thedegritted crude may be centrifuged prior to flotation to control theparticle size distribution such that the subsequent high speedcentrifuge operation results in desired coarse particle sizedistribution that does not require a further centrifuge act.

Flotation is performed in any conventional manner including wetflotation, ultraflotation, froth flotation, TREP flotation (titaniaremoval and extraction process), and the like. General methods offlotation are described in Mathur, S., “Kaolin Flotation”, Journal ofColloid and Interface Science, 256, pp. 153-158, 2002, which is herebyincorporated by reference in this regard. Ultraflotation involves usinga particulate reagent with a fatty acid and selected flotation oils toremove titania from a slurry of impure clay. One characteristic ofultraflotation is that the purified kaolin is recovered as a diluteslurry that is subsequently dewatered. Froth flotation functions byseparating certain mineral particles from other particles in a slurrybased on differences in the mineral species. The processing generallydepends upon adding reagents that selectively attach to mineralparticles to be floated, whereby the particles with attached reagent(s)have a greater affinity for air bubbles than other particles and can beremoved as a froth. TREP flotation involves conditioning kaolin in ahigh intensity mill using a collector, such as a fatty acid collector,tall oil collector, or an hydroxamate collector, and a metal salt. Thisis followed by the addition of a dispersant, such as an acrylate saltdispersant. Optionally, magnetic separation or selective flocculationcan also be used for improving brightness stand alone or in conjunctionwith flotation.

Flotation may be performed at any suitable solids content, pH, andtemperature using a slurry of the degritted kaolin crude and water. Inone embodiment, during flotation at least one of the followingparameters are satisfied: the solids content is from about 10% to about50%, the pH is from about 5 to about 11, and the temperature is fromabout 10° C. to about 90° C. In another embodiment, during flotation atleast one of the following parameters are satisfied: the solids contentis from about 20% to about 40%, the pH is from about 6 to about 10, andthe temperature is from about 20° C. to about 60° C.

In the methods of the present invention, selective flocculation ofkaolin crude is not required to provide the kaolin crude with a discreteparticle size/particle size distribution. In selective flocculation,charged inorganic or organic molecules are used to selectivelyflocculate minerals from each other based on difference in mineralspecies. Selective flocculation of kaolin crude in some instances maydeleteriously affect the brightness and/or viscosity of the resultantkaolin pigment. In one embodiment, the methods of the present inventiondo not comprise selective flocculation of the kaolin crude. In anotherembodiment, the methods of the present invention do not compriseselective flocculation of kaolin until after high-speed centrifugation(discussed below). In yet another embodiment, the methods of the presentinvention do not comprise delaminating kaolin crude.

After flotation, the kaolin undergoing processing is optionallysubjected to ozonation. Ozonation involves oxidative bleaching, usingozone, in order to bleach components, such as organic discolorants, thatmay be present. The ozone acts not only to destroy substantial portionsof discoloring organics, but also destroys by oxidation the organicdispersant, if such a compound is present. However, the ozone does notdestroy inorganic dispersants.

Ozonation is performed in any suitable manner. For example, ozonationmay be performed at a dosage level from about 0.1 to about 20 pounds ofozone per ton of kaolin. In another embodiment, ozonation is performedat a dosage level from about 0.5 to about 10 pounds of ozone per ton ofkaolin. The ozone may be applied as a stream of bubbles which can bepassed upwardly through the slurry. This can be a batch process or acontinuous process in which the ozone bubbles pass counter current to aflow of the slurry in a pipe or other conduit, such as mixed and packedcolumn.

After ozonation, the ozonated kaolin is subjected to optionaldelamination. Delamination can involve wet milling, slurry milling, wetgrinding, and the like. Such delamination processes involve the use of agrinding media and water. Kaolin is combined with the grinding media andwater to form a slurry and transported, such as by pumping, through thedelamination equipment. Typically, the kaolin solids in the slurryduring delamination is from about 5% to about 50% by weight.

After ozonation, high-speed centrifugation is employed to separate theoptionally ozonated kaolin into two streams. It is noted that thehigh-speed centrifugation is performed after flotation. Centrifugationseparates the kaolin into a coarse stream (at least about 70% by weightof the particles have a size of 2 microns or less) and a fine stream (atleast about 80% by weight of the particles have a size of 1 micron orless). In another embodiment, the coarse stream has at least about 80%by weight of the particles have a size of 2 microns or less and the finestream has at least about 85% by weight of the particles have a size of1 micron or less. In yet another embodiment, the coarse stream has atleast about 90% by weight of the particles have a size of 2 microns orless and the fine stream has at least about 90% by weight of theparticles have a size of 1 micron or less.

Although not wishing to be bound by any theory, it is believed thatusage of high-speed centrifuge to generate the ultrafine particle sizedistribution also results in removal of coloring impurities and thusincreasing brightness of the product in excess of about 91 GEB.

All particle sizes referred to herein are determined by a conventionalsedimentation technique using a Micromeretics, Inc.'s SEDIGRAPH® 5100analyzer analysis. The sizes, in microns, are reported as “e.s.d.”(equivalent spherical diameter). Particles are slurried in water with adispersant and pumped through the detector with agitation to disperseloose agglomerates.

Centrifugation may be conducted more than once, but at least onecentrifugation treatment is a high-speed centrifugation treatment. In ahigh-speed centrifugation treatment the centrifuge may operate at “g”forces from above about 1,000 to about 10,000. In another embodiment,the high-speed centrifugation treatment the centrifuge may operate at“g” forces from about 2,000 to about 7,500. In yet another embodiment,the high-speed centrifugation treatment the centrifuge may operate at“g” forces from above about 2,500 to about 5,000. Examples ofcentrifuges include Bird solid bowl machines, high speed centrifuges,horizontal three-phase centrifuges, and the like.

The fine stream is then subject to refining, which may involve at leastone of flocculation, bleaching, filtering, drying, blending, andpulverizing to provide the ultrafine kaolin. Flocculation involvesseparating minerals of one species from minerals of the same species,e.g., the separation of ultrafine kaolin particles from fine or coarsekaolin particles. Flocculation is effected using an ionic material, suchas an acid. Sulfuric acid is an inexpensive and widely available acid.

Generally, bleaching involves increasing the brightness of the kaolin.Bleaching involves contacting the coarse kaolin stream with a suitableamount of one or more of hydrosulfite (dithionite) salts, potassiumpermanganate, oxygen gas, alkali bichromates, alkali chlorates, alkalichlorites, ammonium persulfate and soluble peroxides such as sodium andhydrogen peroxide, sodium hypochlorite, and the like.

Filtration can be employed to at least one of increase solids content(for example increase solids content to about 55% or higher) and tosubstantially remove particles larger than 2 microns. Increasing thesolids content in some instances improves the efficiency of a subsequentspray drying operation. Filtration can be carried out in any suitablemanner and is typically carried out using rotary drum vacuum filters.

Drying, such as spray drying, the kaolin is performed to reduce themoisture level of the kaolin. Drying the kaolin may facilitate optional,subsequent pulverization acts. The kaolin is dried by any suitabletechnique. Examples of drying kaolin include spray drying, flash drying,rotary drying, or other conglomeration techniques. These dryingtechniques are known in the clay industry. In one embodiment, afterdrying the ultrafine kaolin has a moisture level of less than about 1.5%by weight. In another embodiment, after drying the ultrafine kaolin hasa moisture level of less than about 1% by weight. In yet anotherembodiment, after drying the ultrafine kaolin has a moisture level ofless than about 0.5% by weight.

Blending involves combining the kaolin with other particulate matter,such as a different batch of kaolin, titania, other clays, calciumcarbonate, calcined kaolin, and the like to arrive at a mixture that hasproperties desired by the end user or a subsequent user.

Pulverization may be conducted in any suitable manner. In oneembodiment, the ultrafine kaolin is pulverized in at least once. Inanother embodiment, the ultrafine kaolin is pulverized in at least twoseparate acts (twice pulverized). The pulverization may break up anyagglomerates that may be present. Such agglomerates may form duringdrying, changing the particle size achieved by high-speed centrifugationand other process acts.

The ultrafine kaolin pigment product has numerous desirable properties.For example, the ultrafine kaolin pigment product has one or more of atleast about 97% by weight of the particles have a size of 2 microns orless, at least about 96% by weight of the particles have a size of 1micron or less, at least about 89% by weight of the particles have asize of 0.5 microns or less, at least about 67% of the particles have asize of 0.3 microns or less, a surface area of at least about 23 m²/g,about 0.75% by weight or less of titania, about 1.5% by weight or lessof iron oxide, and brightness of about 91 or more. In anotherembodiment, the ultrafine kaolin pigment product has one or more of atleast about 98% by weight of the particles have a size of 2 microns orless, at least about 97% by weight of the particles have a size of 1micron or less, at least about 90% by weight of the particles have asize of 0.5 microns or less, at least about 70% of the particles have asize of 0.3 microns or less, a surface area of at least about 25 m²/g,about 0.5% by weight or less of titania, about 1.25% by weight or lessof iron oxide, and brightness greater than 92. In yet anotherembodiment, the ultrafine kaolin pigment product has one or more of atleast about 99% by weight of the particles have a size of 2 microns orless, at least about 98% by weight of the particles have a size of 1micron or less, at least about 92% by weight of the particles have asize of 0.5 microns or less, at least about 72% of the particles have asize of 0.3 microns or less, a surface area of at least about 26 m²/g,about 0.4% by weight or less of titania, about 1% by weight or less ofiron oxide, and brightness of about 93 or more.

Surface area is determined by the art recognized BET method using N₂ asthe adsorbate. Surface area alternatively is determined using GardnerColeman Oil Absorption Test is based on ASTM D-1483-84 which measuresgrams of oil absorbed per 100 grams of kaolin. Brightness measurementsare performed using the TAPPI standard method, T524, and are reported as“GE brightness” or “GEB values”.

The coarse stream is then subject to refining which may involve at leastone of bleaching, filtering, bulking, spray drying, and blending.Blending involves combining the coarse kaolin with other particulatematter, such as a different batch of kaolin, titania, other clays,calcium carbonate, calcined kaolin, and the like to arrive at a mixturethat has properties desired by the end user or a subsequent user.

The coarse kaolin pigment product has numerous desirable properties thatmake it particularly useful in paper coating applications. For example,the coarse kaolin pigment product has one or more of at least about 95%by weight of the particles have a size of 5 microns or less, at leastabout 80% by weight of the particles have a size of 2 microns or less,at least about 20% by weight of the particles have a size of 0.3 micronsor less, a surface area from about 14 to about 20 m²/g, about 1% byweight or less of titania, about 1.5% by weight or less of iron oxide,and a brightness of about 85 or more. In another embodiment, the coarsekaolin pigment product has one or more of at least about 96% by weightof the particles have a size of 5 microns or less, at least about 90% byweight of the particles have a size of 2 microns or less, at least about25% by weight of the particles have a size of 0.3 microns or less, asurface area from about 15 to about 19 m²/g, about 0.75% by weight orless of titania, about 1.25% by weight or less of iron oxide, and abrightness of about 87.5 or more.

Generally speaking, one or more conventional clay processing steps suchas crushing, grinding, frationation, delamination, magnetic separation,floc/filtration, heat treatment, and the like, may be employed before orafter the methods of the present invention.

Crushing reduces kaolin rock to gravel; that is, kaolin rock havingdiameters of less than about 10 cm in diameter. Grinding involvesprocessing crude kaolin to achieve a desired particle size distribution.Grinding may be carried out by dry milling, dry ball milling, drygrinding, and the like.

Kaolin contains naturally separated platy kaolin particles as well as“booklets”, which comprise stacks of kaolin platelets. These stacks areconcentrated in particles having a size of about 2 or more microns.Delamination of these booklets involves providing impact energy which isjust sufficient to cleave apart the kaolin platelets that make up thebooklets without further fracturing the kaolin platelets. Delaminationcan involve wet milling, slurry milling, wet grinding, and the like.Such optional delamination processes involve the use of a grinding mediaand water. Kaolin is combined with the grinding media and water to forma slurry and transported, such as by pumping, through the delaminationequipment. Typically, the kaolin solids in the slurry duringdelamination is from about 5% to about 50% by weight.

Kaolin may be optionally subjected to one or more heat treatments. Whenkaolin is heated, it undergoes a series of characteristic changes,detectable by various methods including differential thermal analysis(DTA). Heat treatment may be employed to form one or more of metakaolin,partially calcined kaolin, and calcined kaolin, depending on thetemperature/duration of the heat treatment. Heat treatment is performedunder one of an inert atmosphere, an oxidizing atmosphere, and areducing atmosphere.

For example, after heating from about 450 to about 650° C. for asufficient period of time, kaolin undergoes a strongly endothermicdehydration reaction resulting in the conversion to material known asmetakaolin. The metakaolin state is conveniently ascertained by acidsolubility testing because the alumina in the clay is virtuallycompletely soluble in strong mineral acid.

Calcining destroys the crystallinity of hydrous kaolin and renders thekaolin substantially amorphous. Calcination occurs after heating attemperatures in the range from about 700 to about 1200° C. for asufficient period of time. Commercial vertical and horizontal rotarycalciners can be used to produce metakaolin, partially calcined kaolin,and/or calcined kaolin. Operation is controlled to avoid calcining atsufficiently high temperatures to form unwanted mullite (3Al₂O₃·SiO₂).

Referring to FIG. 1, a high level diagram of various aspects of anultrafine kaolin processing methodology 100 is shown. In act 102, kaolincrude containing at least a super majority of gray kaolin is optionallydegritted, removing relatively large particles from the gray kaolincrude. After relatively large particles are removed from the gray kaolincrude, act 104 involves flotation to reduce the amount of at least oneof titania and/or iron oxide in the degritted kaolin. Act 106 involvesoptionally ozonating the kaolin. After ozonation, act 108 involvescentrifuging at high speeds the kaolin and thereby separating the kaolininto two different grades/streams. The coarse stream produced by act 108is subjected to additional processing such as refining and then employedin paper applications 110. In act 112, the fine stream from act 108 issubject to refinement, such as flocculation, bleaching, filtration, andspray drying, to produce an ultrafine kaolin stream. The ultrafinekaolin is optionally subject to pulverization 116 to provide theultrafine kaolin pigments 116.

Referring to FIG. 2, a system 200 to process gray kaolin crude intoultrafine kaolin is shown. The system 200 includes one or more of adegrit system 202 for degritting crude kaolin, a flotation system 204,an ozonation system 206, and a high-speed cetrifugation system 208, atleast one of which is coupled to a tester 210 and a processor-controller212. The degrit system 202 processes gray crude kaolin by removing largegrit from the kaolin crude, the flotation system 204 reduces the titaniaand or iron oxide content of the degritted kaolin, the ozonation system206 oxidizes species within the kaolin process stream, and thehigh-speed cetrifugation system 208 separates two distinct kaolinstreams from each other (fine and coarse). The tester 210 can be anydevice that measures at least one parameter associated with the kaolinbeing processed (such as particle size distribution, surface area,brightness, whiteness, roughness, % moisture content, % content ofparticular chemical such as titania, and the like) or any parameterassociated with any one of the degrit system 202, flotation system 204,ozonation system 206, and high-speed cetrifugation system 208 (such asthe particle size and/or “g’ force with the high-speed cetrifugationsystem 208).

While any one of the degrit system 202, flotation system 204, ozonationsystem 206, and high-speed cetrifugation system 208 are operating, thetester 210 tests the kaolin being processed. For example, while thedegrit system 202, flotation system 204, or ozonation system 206 isoperating, a sample of kaolin may be withdrawn and tested to determine aparameter, such as particle size distribution. The tester 210 sends thedata generated by the testing to the processor-controller 212, which isadapted to receive such kaolin parameter data from the tester 210.Alternatively, the tester 210 may measure a parameter of the degritsystem 202, flotation system 204, ozonation system 206, andcetrifugation system 208, and send data associated with the parameter tothe processor-controller.

The processor-controller 212 analyzes such data, and based on theanalysis, sends a signal to any of the degrit system 202, flotationsystem 204, ozonation system 206, and cetrifugation system 208 to eithercontinue the process, modify the process, or terminate the process. Tofacilitate such analysis, a data store or memory 214 may be coupled tothe processor-controller 212 so that the processor-controller 212 cancompare data sent by the tester 210 to stored data. Theprocessor-controller 212 may send a signal to the tester 210 to performa test. Examples of ways in which the processor-controller 212 canmodify a process include increasing or decreasing the “g” forces in thehigh-speed cetrifugation system 208; increasing or decreasing thetemperature in the flotation system 204; increasing or decreasing thework/energy required by any of the degrit system 202, flotation system204, ozonation system 206, and/or cetrifugation system 208; continueoperating or terminate any of the degrit system 202, flotation system204, or ozonation system 206 to achieve a certain desired particle sizedistribution; and the like. Consequently, the system 200 can providereal time analysis and real time feed back, so that the processing ofkaolin can be modified in real time to suit immediately existing needs.

The present invention further relates to paint compositions containingmajor amounts of a paint vehicle and minor amounts of the ultrafinehydrous kaolin described herein. Major amounts include at least 50%(percent volume of dry paint film) whereas minor amounts include lessthan 50% (percent volume of dry paint film). The paint vehicle may beany one of a latex paint vehicle, oil based paint vehicle, alkyd paintvehicle, acrylic paint vehicle, styrene paint vehicle, and/or epoxypaint vehicle. The paint vehicle contains components suitable forforming a paint film. Most often, the ultrafine hydrous kaolin describedherein functions as a pigment extender or pigment.

Paint compositions may be made in any suitable manner. For example, thecomponents may be combined and mixed. The components may be combined allat once, or sequentially.

In one embodiment, the paint compositions of the present inventioncontain from 50% to about 99.99% (percent volume of dry paint film) of apaint vehicle and from about 0.01% to about 49% (percent volume of drypaint film) of the ultrafine hydrous kaolin. In another embodiment, thepaint compositions of the present invention contain from about 60% toabout 99.9% (percent volume of dry paint film) of a paint vehicle andfrom about 0.1% to about 40% (percent volume of dry paint film) of theultrafine hydrous kaolin. In yet another embodiment, the paintcompositions of the present invention contain from about 70% to about99% (percent volume of dry paint film) of a paint vehicle and from about1% to about 30% (percent volume of dry paint film) of the ultrafinehydrous kaolin.

In one embodiment, the ultrafine hydrous kaolin described herein may beused as a pigment extender with titania as a pigment in a paintcomposition. In another embodiment, the paint compositions of thepresent invention contain from 50% to about 99.9% (percent volume of drypaint film) of a paint vehicle, from about 0.1% to about 40% (percentvolume of dry paint film) of titania, and from about 0.1% to about 40%(percent volume of dry paint film) of the ultrafine hydrous kaolin. Inyet another embodiment, the paint compositions of the present inventioncontain from about 60% to about 98% (percent volume of dry paint film)of a paint vehicle, from about 1% to about 30% (percent volume of drypaint film) of titania, and from about 1% to about 30% (percent volumeof dry paint film) of the ultrafine hydrous kaolin. In still yet anotherembodiment, the ultrafine hydrous kaolin described herein may be used asa pigment extender with other pigment extenders such as one or more ofclays, carbonates, talc, and silicas with or without titania as apigment in a paint composition.

One parameter in paint formulation is the pigment volume concentration(hereinafter PVC). PVC is a control factor in the design of paintformulations, because paint properties are generally governed by volumerather than weight effects. The following equation defines the PVC as apercentage of volume of dried paint film:

% PVC=100×V _(pigment) /V _(total)

where V_(pigment) is the volume of the pigment and other non-volatilesin the dried paint film and V_(total) is the V_(pigment) plus the volumeof the paint vehicle/resin. The critical pigment volume concentration(hereinafter CPVC) is defined as that PVC at which air interfaces aregenerated in the dry paint film due to the deficiency of binder withrespect to pigment. It is well known that many paint volume propertieschange drastically at CPVC. Typically, the relationship between PVC andCPVC is nonlinear. In many instances, different paints are properlycompared on the basis of equal reduced pigment volume concentration(hereinafter RPVC). The RPVC is defined by the following equation:

RPVC=PVC/CPVC

Generally gloss grade paints, either exterior or interior have an RPVCof less than about 1.

CPVC is related inversely to the amount of binder that the pigmentparticles “absorb.” One technique to measure the absorption potential ofa pigment or extender is to determine the amount of linseed oil neededto form a paste with a given weight of pigment. This may be referred toas oil absorption. As used herein the term “oil absorption” refers tothe procedure described in ASTM D 281. Generally speaking, substitutionof an equal amount of high oil absorption extender pigment for one oflow oil absorption results in a reduction of the CPVC of that paint.This is turn restricts the range of PVC that can be utilized in exteriorformulations as well as the amount of extender pigment, which can beemployed.

Paints with PVC below critical, such as semi- and high-gloss paints,have no entrapped air in the dry film. The entire solid surface iswetted by the binder and opacity is obtained solely by pigment andpigment extender particles. At any given particle concentration, opacityis improved or optimized by ensuring maximum surface exposure of thepigment and pigment extender particles to light. Using the ultrafinehydrous kaolin of the present invention as a pigment extender with aparticle size similar to the pigment facilitates desirable spacing ofthe pigment particles, prevents agglomeration of the pigment particles,and ensures maximum exposure to light.

Above the CPVC, paints are considered matte. The degree of matteness isdetermined by 85 deg gloss, or what is commonly known as the sheen.Below the CPVC, paints are glossy and are considered as eithersemi-gloss or high gloss. Gloss is typically measured at 60 deg or 20deg angles.

The structure (PSD, surface area) the ultrafine hydrous kaolin of thepresent invention facilitates gloss retention and efficient pigmentspacing. In one embodiment, the ultrafine hydrous kaolin of the presentinvention has a similar size to titania and fits in desirably betweenthe dispersed titania particles/agglomerates. In other words, theultrafine hydrous kaolin extender works generally as a pigment extender,and specifically as a TiO₂ pigment spacer, which maximizes exposure ofthe pigment surface such as TiO₂ to light, resulting in higher opacity.

High gloss and semi gloss grade paints contain a mixture of primepigment and extender pigment with titanium dioxide often used as theprime pigment because of its outstanding optical properties. The mostcommonly used extender pigments for latex and alkyd paints are hydrouskaolin and finer grades of calcium carbonate and talc. The binder inemulsion paints consists of globules (typically from about 0.1 to about1.0 micron diameter) of a film-forming polymer having a molecular weightfrom about 10,000 to about 1,000,000. The latex particle size andcomposition are varied to effect changes in such properties asdurability, gloss, glass transition temperature and the like. Atpresent, acrylic and vinyl-acrylic resins account for the majority ofbinders used in latex paints.

Conventionally, it is believed in the paint industry that increasing thesurface area of ultrafine kaolin pigment adversely affects the glossperformance of the paint at low PVC and below CPVC. However, theinventors unexpected discovered that a high surface area ultrafinehydrous kaolin pigment can provide gloss performance equal to or betterthan any other hydrous kaolin pigment available commercially.

The reasoning behind this discovery is as follows. The glossingkaolin-based products with 90-91 GEB are typically produced in thekaolin industry using a tertiary crude such as from East Georgia andsubjecting it a selective flocculation beneficiation process. Oneglossing kaolin product, Polygloss® 90 available from J.M. HuberCorporation, believed to be produced through such a process, providesthe highest gloss among the commercial pigments available in a number ofpaint and industrial coatings applications. The ultrafine kaolin of thepresent invention has a finer PSD and a higher surface area thanPolygloss® 90 and unexpectedly resulted in higher gloss withoutcompromising the hiding power of the paint film.

The following examples illustrate the present invention. Unlessotherwise indicated in the following examples and elsewhere in thespecification and claims, all parts and percentages are by weight, alltemperatures are in degrees Centigrade, and pressure is at or nearatmospheric pressure.

EXAMPLE 1

Table 1 shows the typical characteristics of a gray crude thatfacilitates successful execution of the present invention. Also listedare characteristics of a specific gray kaolin crude (Example 1) that isused to illustrate the present invention in Examples 2 and 3.

TABLE 1 Property Typical values Example 1 GE Brightness 80-85 82.6Surface area min 18 (m²/g) 20 (m²/g) % TiO₂ 1.6-2   1.81 % Fe₂O₃ 0.7-1.10.9 Particle size, % mass finer than   2 μm 80 82 0.3 μm 35 38

EXAMPLE 2

The crude from Example 1 is subjected to degritting, ultraflotation,ozonation, and high-speed centrifuge separation to result in a finestream and a coarse stream. Flotation is conducted so as to reduce theTiO₂ content to less than 0.7%. The centrifuge is operated underconditions to target 18-22% less than 0.3 μm particle size whichtypically results in 74-78% less than 2 μm particle size. The coarsestream is further subjected to a second centrifuge act so as to recover90% less than 2 μm particles. The characteristics of the coarse streamsubjected to a second centrifuge act and the fine stream from the firstcentrifuge act are shown in Table 2.

TABLE 2 Property Fines following centrifuge GE Brightness 91.2 Surfacearea (m²/g) 26.2 % TiO₂ 0.29 % Fe₂O₃ 0.89 Particle size, % mass finerthan   2 μm 100 0.3 μm 71

EXAMPLE 3

The ultrafines in Table 2 are flocced using sulfuric acid, bleached, andfiltered. The filter cake is dispersed with a specified blend of sodaash/polyacrylate/phosphate, and spray dried. The spray dried product ispulverized to a Hegman grind of 6.5. The characteristics of theultrafine product (UF I) of the present invention along with acomparison of a commercial Polygloss® 90 kaolin pigment are providedbelow in Table 3. Also, included is the product ASP® Superfine hydrousaluminosilicate produced using a selective flocculation process byEngelhard Corporation.

TABLE 3 Properties Polygloss ® 90 UF 1 ASP ® Superfine Surface Area(m²/g) 22 26 22.5 TAPPI Brightness, % 90.0 91.7 91.3 Particle SizeDistribution Mass % finer than   2 μm 97 99 99   1 μm 96 98 96 0.5 μm 8692 88 0.3 μm 60 72 66

EXAMPLE 4

Example 4 demonstrates a solvent neutral base clear alkyd paintformulation. UF I prepared in accordance with Example 3 is tested in agloss paint application. Paint formulations of Examples 4 to 9 are basedon 100 gallons volume and an amount of raw materials in pound per 100gallons. In the solvent paint there is no adverse impact on gloss inspite of the finer particle size and surface area of the UF I comparedto Polygloss® 90.

Solvent Neutral Clear Base Alkyd Paint Formulation

Raw Material Amount Gallon VT Alkyd 6693 153.8 20.6 Mineral Spirits 36.45.6 Tixogel 8.0 0.1 Ethanol 3.0 0.5 Mix until smooth Lecithin 5 2.0 0.2Lo-529 2.0 0.2 Anti-Float Powder 6.0 0.5 Kaolin 40.0 1.9 BYK 370 1.0 0.1Grind to 7 Hegman, then add VT Alkyd 6693 380.0 51.0 VM&P 62.0 9.9Cobalt 12% 1.0 0.1 Zirco 24% 3.0 0.3 Exkin #2 1.0 0.1 Hold for ViscosityVM&P 56.0 8.9 Total 755.2 100.0

Comparative Gloss and Sheen Data of UF I and Polygloss® 90

Properties Polygloss ® 90 UF I 20 degree Gloss: 73.3 73.5 60 degreeGloss: 91.7 91.7 85 degree Sheen: 96.1 96.5

EXAMPLE 5

Example 5 demonstrates an Interior semigloss latex paint formulation. UFI prepared in accordance with Example 3 is tested in another gloss paintapplication. In the latex paint there is significant improvement ingloss with UF I compared to that due to Polygloss® 90.

Interior Semigloss Latex Paint Formulation PVC-22, Low VOC

Raw Material Amount Gallon Water 145.0 17.4 KTPP 1.0 0.1 Kathon LX 1.50.2 Natrosol Plus 330 1.0 0.1 Tamol 1124 5.0 0.6 Triton CF 10 3.0 0.3AMP 95 2.0 0.3 Rhodoline 643 1.0 0.1 Mix it for 2 min., then add TiO₂-CR828 240.0 7.2 Kaolin 20.0 0.9 Attagel 50 5.0 0.3 Grind 6 to 7, then addWater 113.1 13.6 UCAR 300 500.0 56.2 Strodex PK 90 2.0 0.2 Ammonia 2.50.3 Polyphobe TR 116 1.0 0.1 Polyphobe TR 117 18.0 2.0 Rhodoline 643 2.00.3 Total 1063.1 100.0

Comparative Evaluation b/t UF I and Polygloss® 90 Semi Gloss PaintPVC-22

Properties UF I Polygloss ® 90 Viscosity KU @ 77° F. 80 82 pH: 8.3 8.4C. Ratio 3 mils: 98.7 98.5 Reflectance: 92.3 93.1 Whiteness: 88.2 88.6Yellowness: 1.6 1.5 Hunter L: 97.5 97.6 Hunter a: −0.9 −1.0 Hunter b:1.3 1.2 Gloss @ 60 deg: 65.1 55.2 Sheen @ 85 deg: 91.8 88.7 Gloss @ 20deg: 23.1 14.7

EXAMPLE 6

Example 6 demonstrates a water reducible high gloss alkyd enamel paintformulation. UF 1 prepared in accordance with Example 3 is tested in ahigh gloss paint application. In a water reducible alkyd high glossenamel paint, there is significant improvement in the 20 degree glossvalue compared to Polygloss® 90.

Reducible High Gloss Alkyd Enamel Paint Formulation PVC-16

Raw Material Amount Gallon Beckosol 10-060 (70%) 72.0 9.0 MineralSpirits 9.3 1.4 Bentone SD-1 1.5 0.1 Mix well, then add: LDA 100Polymeric Dispersant 2.0 0.3 Hex-Cem Calcium Octoate 10% 3.0 0.4TiO₂-R-706 110.0 3.3 UF I/Polygloss ® 90 15.0 0.7 Grind to 7, then addBeckosol 10-060 (70%) 44.5 5.6 Mineral Spirits 18.0 2.8 Mix it well,then add Beckosol 10-060 (70%) 130.0 16.3 Mineral Spirits 92.4 14.2Cobalt Octoate 12% 1.0 0.1 Zirconium Octoate 12% 4.0 0.5 Skine # 2 1.00.1 Mix well, then add under agitation: LPR 76, Polysach. Resin 44% 40.04.0 Water 344.3 41.3 Mix for 30 min.: Total 888.0 100.0

Comparative Evaluation b/t UF I and Polygloss® 90 in High Gloss AlkydEnamel Paint Formulation PVC-16

Properties UF I Polygloss ® 90 Viscosity KU @ 77° F. 91 92 C. Ratio 3mils: 92.3 91.9 Reflectance: 87.2 87.0 Whiteness: 77.7 77.3 Yellowness:4.2 4.3 Hunter L: 95.9 95.9 Hunter a: −1.2 −1.2 Hunter b: 2.7 2.8 Gloss@ 60 deg: 78.8 75.1 Sheen @ 85 deg: 98.3 97.6 Gloss @ 20 deg: 41.5 31.4

EXAMPLE 7

Example 7 demonstrates a interior/exterior gloss paint formulation. UF 1prepared in accordance with Example 3 is tested in another high glosspaint application. In a styrene acrylic high gloss waterborne paint, UF1 exhibited higher 20 and 60 degree gloss values compared to Polygloss®90.

Interior/Exterior Gloss Paint PVC-18.7

Raw Material Amount Gallon Water 62.6 7.5 Kathon LX 1.5% 1.6 0.2 Tamol1124 5.5 0.6 Surfynol 104E 1.0 0.1 Igepal CTA-639W 1.0 0.1 BYK-022 1.00.1 Mix for 2 min., then add Ti Pure-R 706 202.5 6.1 Kaolin 14.5 0.7Grind 6 to 7, then add Propylene Glycol 30.28 3.5 Rhoplex HG-700 618.170.0 Water 21.45 2.6 Texanol 21.5 2.7 Triton X 405 3.5 0.4 Ammonia 1.00.1 Pre mix following three, then add Water 22 2.6 Acrysol RM 5 22 2.4BYK-024 2.0 0.3 Total 1031.5 100.0

Comparative Evaluation b/t UF I and Polygloss® 90 in Interior/ExteriorGloss Paint PVC-18.7

Properties UF I Polygloss ® 90 Viscosity KU @ 77° F. 94 95 pH 8.4 8.4 C.Ratio 3 mils: 98.2 98.2 Reflectance: 94.5 94.5 Whiteness: 91.0 91.0Yellowness: 1.1 1.1 Hunter L: 98.0 98.0 Hunter a: −0.8 −0.8 Hunter b:0.9 0.9 Gloss @ 60 deg: 78.5 77.8 Sheen @ 85 deg: 93.4 93.1 Gloss @ 20deg: 52.3 51.5

EXAMPLE 8

Example 8 demonstrates a gloss white enamel paint formulation. UF 1prepared in accordance with Example 3 is tested in another high glosspaint application. In another styrene acrylic enamel paint, 10% TiO₂ isextended with volume amount of UF 1 by keeping the PVC of the paintsame. UF 1 unexpectedly exhibited similar opacity and gloss performancecompared to paint having 100% TiO₂. UF 1 also showed higher gloss in thepaint than Polygloss® 90.

Gloss White Enamel Paint PVC-17.6

(−) 10% TiO₂ by Control 100% TiO₂ kaolin volume Raw Material AmountGallon Amount Gallon Water 169.2 20.3 169.2 20.3 Kathon LX 1.5% 3.0 0.43.0 0.4 KTPP 0.5 0.1 0.5 0.1 Tamol 1124 3.5 0.4 3.5 0.4 Propylene Glycol26.0 3.0 26.0 3.0 Surfynol 104H 1.0 0.1 1.0 0.1 BYK-022 1.0 0.1 1.0 0.1Acrysol TT 935 8.0 0.9 8.0 0.9 Ammonia 2.0 0.3 2.0 0.3 Mix it for 2min., then add CR 828 225.0 6.8 202.5 6.1 Hydrous Kaolin 0.0 0.0 14.50.7 Grind 6 to 7, then add Stordex PK 90 1.0 0.1 1.0 0.1 Ucar 471 516.159.6 516.1 59.6 Texanol 20.0 2.5 20.0 2.5 Water 20.7 2.5 20.7 2.5Synthesizer 160 10.0 1.1 10.0 1.1 Acrysol RM 5 15.0 1.7 15.0 1.7 BYK-0242.0 0.3 2.0 0.3 Total 1024.0 100.0 1016.0 100.0

Comparative Evaluation b/t UF I and Polygloss® 90 in Gloss White EnamelPaint PVC-17.6

100% TiO₂ (−) 10% TiO₂ (−) 10% TiO₂ Properties Control UF I Polygloss ®90 Viscosity KU @ 77° F. 96 97 95 pH 8.6 8.5 8.5 C. Ratio 3 mils: 98.097.8 97.8 Reflectance: 94.4 93.8 93.7 Whiteness: 91.1 90.1 90.1Yellowness: 0.5 0.7 0.7 Hunter L: 97.9 97.8 97.8 Hunter a: −0.9 −0.9−0.9 Hunter b: 0.8 1.0 1.0 Gloss @ 60 deg: 75.1 75.3 74.6 Sheen @ 85deg: 93.4 93.4 92.6 Gloss @ 20 deg: 39.2 38.1 37.2

EXAMPLE 9

Example 9 demonstrates a two part waterborne epoxy coating formulation.UF 1 prepared in accordance with Example 3 is tested in another highgloss paint application. In the high gloss waterborne epoxy paintformulation, there is improvement in 20 degree gloss value with UF 1,when compared with Polygloss® 90.

Two Part Waterborne Epoxy Coating PVC-22.7, Usable Pot Life—6 hrs

Raw Material Pounds Gallons Part-A EPI-REZ Resin 3520-WY-55 329.4 36.0Water 116.3 14.0 Total Part A 445.7 50.0 Part-B EPI-CURE Curing Agent8536-MY-60 160 19.3 Agitan 731 2.0 0.2 TiO₂-R 900 250 7.5Kaolin-Polygloss ® 90/UF I 30 1.4 Grind at High speed to 6 to 7, thenadd EPI-CURE Curing Agent 8536-MY-60 22.5 2.7 Glacial Acetic Acid 2.30.3 Water 155.4 18.7 Total Part B 622.2 50.0 Composite Blend Part-A445.7 50.0 Part-B 621.9 50.0 Total Part A and B 1067.6 100.0

Comparative Evaluation b/t UF I and Polygloss® 90 in Two Part WaterborneEpoxy Coating PVC-22.7

Properties UF I Polygloss ® 90 Viscosity KU @ 77° F. 118 119 C. Ratio 3mils: 97.2 97.0 Reflectance: 90.3 90.2 Whiteness: 81.5 81.7 Yellowness:3.9 4.1 Hunter L: 97.1 97.1 Hunter a: −1.2 −1.2 Hunter b: 2.5 2.7 Gloss@ 60 deg: 100 100 Sheen @ 85 deg: 97.3 97.0 Gloss @ 20 deg: 98.8 97.7

While the invention has been explained in relation to certainembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

1. A method of processing kaolin, comprising sequentially: subjecting akaolin crude comprising a super major amount of gray kaolin to flotationto provide a kaolin having reduced titania content; centrifuging thekaolin kaolin having reduced titania content at high speeds to provide acoarse stream and fine stream, the coarse stream comprising kaolinwherein at least about 70% by weight has a size of 2 microns or less,the fine stream comprising kaolin wherein at least about 80% by weighthas a size of 1 micron or less; and refining the fine stream into anultrafine kaolin pigment.
 2. The method of claim 1, wherein centrifugingat high speeds involves using “g” forces from about 1,000 to about10,000.
 3. The method of claim 1, wherein the kaolin crude comprises atleast about 75% by weight of gray kaolin.
 4. The method of claim 1,wherein flotation reduces the titania content of the kaolin to less thanabout 1% by weight.
 5. The method of claim 1, wherein flotationcomprises one of froth flotation, ultraflotation, and TREP flotation. 6.The method of claim 1, further comprising degritting the kaolin crudebefore subjecting the kaolin crude to flotation.
 7. The method of claim1 further comprising ozonating the kaolin having a reduced titaniacontent before centrifuging the kaolin, ozonating comprising contactingthe kaolin having a reduced titania content with about 0.1 to about 20pounds of ozone per ton of kaolin.
 8. The method of claim 1, whereinrefining the fine stream comprises at least two of flocculation,bleaching, filtering, and drying.
 9. The method of claim 1, whereinrefining the fine stream comprises at least three of flocculation,bleaching, filtering, spray drying, and pulverization.
 10. The method ofclaim 1, with the proviso that the method does not comprise selectiveflocculation of the kaolin crude.
 11. The method of claim 1 furthercomprising refining the coarse stream into a coarse engineered kaolinpigment.
 12. The method of claim 1, further comprising testing andgenerating data of at least one parameter of at least one of the kaolincrude, the kaolin having reduced titania content, the fine stream, orultrafine kaolin pigment or at least one parameter of subjecting thekaolin crude to flotation and centrifuging the kaolin at high speeds;and controlling operation of at least one of subjecting the kaolin crudeto flotation and centrifuging the kaolin at high speeds based on datagenerated by the tester. 13-20. (canceled)